The present invention relates to a device for transforming a rotational movement into a linear movement.
A typical prior art device of this type is shown in Uhing U.S. Pat. No. 2,940,322 issued June 14, 1970 entitled ROTARY TRANSLATORY DRIVE GEAR. This device comprises an elongated casing having a rotatable shaft extending therethrough and a series of rings mounted in the casing having a bore diameter larger than the diameter of the shaft and contacting the shaft at axially spaced locations. The rings are the inner ring of ball bearings. Means in the form of intermeshing gears are provided to selectively rotate the inner rings to vary the angular position in relation to the shaft. By this arrangement with the rotational axis of the rotatable inner rings disposed at an angle to the shaft axis, there results as a consequence of the speed of rotation of the shaft and the speed of rotation of the rings, a shift thrust component acting between the shaft and the rings extending axially of the shaft. This component therefore will affect axial movement of the casing on the shaft upon rotation of the shaft or rotation of the shaft upon axial movement of the casing. The bearings are pivotally supported in the casing by pads at diametrically opposed locations which mount pins extending through the casing wall.
An important consideration in devices of this type is the mounting arrangement for the bearings to facilitate tilting or skewing in the casing or retainer in a simple and reliable manner. Furthermore, these components should possess sufficient physical strength in a relatively simple assembly so that it is also economical to manufacture.